Female reproductive senescence is marked by the progressive loss of ovarian function, menstrual regularity and endocrine homeostasis. Reproductive aging is accompanied by vasomotor and urogenital symptoms preceding the event of menopause itself, and can contribute to pathophysiological syndromes including osteoporosis and cardiovascular disease. Population and genetic studies of nonhuman primates will enhance how we understand perimenopause - the menopausal transition. Female baboons of SFBR in particular offer a unique model to understand human reproductive aging because we can accurately determine their life-long menstrual behavior from perineum turgescence and, like humans, are non-seasonal breeders. This Project will study individual menstrual dynamics to quantify the state of reproductive senescence for all females of the large study population, and it will generate detailed profiles of daily individual multi-cycle gonadotropic and steroid hormones. These measures will provide individual based estimates on a population scale to estimate the contribution of environment, maternal and genetic components to variation reproductive aging, and to identify genetic loci that influence reproductive patterns and perimenopause. The data will provide unique opportunities to evaluate mechanistic models for perimenopause. Coupled with the program-wide multidimensional measures of somatic aging, we shall evaluate the extent that reproductive and somatic aging are concordant or independent.